G13 keep the genetics secret for PE don't they. Surely must have skunk number 1 in it though somewhere - which is where the cheese strain comes from.
I've had a random cheesy pheno from a strain with skunk 1 hidden deep in its genetics, rare pheno too from what I can gather. Kolossus from Sannies seeds was the strain. I've grown a total of 15 of them now, and the cheesy pheno has only appeared once. The others are so different (citrus/haze) that it really stood out. Others who had a chance to check it out all asked if it was cheese. I've got another little one vegging now in the hope she will be the cheese pheno, we shall see.